1. Field of the Invention
The present invention relates to an electronic equipment system with detachable expander and a power source processing method therefor.
2. Related Background Art
Among such electronic equipment system, there has been proposed a notebook personal computer, wherein it's functions can be expanded by docking an expander incorporating an expansion board.
Such a notebook personal computer with expander is constructed so as to extend the operation time in the portable use, such that it is operable as a dual battery system by extracting the floppy disk drive of the personal computer and inserting a second battery.
In recent notebook personal computers, the portability is considered important not only in the state of the notebook personal computer but also in the state coupled with the expander, so that it is desired to extend the battery-driven time in the state coupled with the expander.
For achieving such extension of the battery-driven time, it is conceivable to employ the second battery of a large capacity or even to employ a third battery, but, for such purpose, a connection space for the battery has to be secured on the expander.
FIGS. 21A and 21B show the configurations of the power source in the conventional notebook personal computer, wherein FIG. 21A shows a case of power supply to the expander from the power source circuit (DC/DC circuit) of the personal computer, while FIG. 21B shows a case in which power source circuits (DC/DC circuits) are respectively provided in the personal computer and the expander.
In the case shown in FIG. 21A, the docking connector has to be provided with power supply lines of a number allowing the supply of a current of maximum consumption. Also a signal line for controlling the battery of the expander from a power source controlling microcomputer (PMC) has to be secured in the docking connector. Also the docking connector loses the compatibility in case the maximum current consumption increases in the future by the increase of functions of the personal computer or the expander.
On the other hand, in the configuration shown in FIG. 21B, since the expander is provided with a power source circuit similar to that in the personal computer, the power supply lines can be maintained minimum though the cost increases by a certain amount. Also this configuration can flexibly adapt to the increase of the maximum current consumption in the future. The power source controlling microcomputer (PMC) of the personal computer often supports, in addition to the control of the power source system, other functions such as the keyboard control. In the docking, therefore, the power source systems have to be combined so as not to detrimentally affect such other functions. Also the power source modes of both power source controlling microcomputers have to be mutually synchronized in order to extend the battery-driven time in the docking state.